1. Field of the Invention
The present invention relates to a chip scale package structure, and more particularly to a chip scale package structure for an image sensor.
2. Description of Related Art
The current package technology of an image sensor usually use the ceramic leaded chip carrier (CLCC) or plastic leaded chip carrier (PLCC) that needs the processes of embedding a die pad and wire bonding. However, the number of I/O pins of an electric element become great, the thickness of the electric element becomes thin and the volume of the electric element becomes small under the requests of a slight weight, multi-function and a quick process speed. Consequently, the conventional solder technology is limited due to the diameter of the holes in the PCB for receiving the leads of electric parts. The surface mounting technology (SMT) is provided to overcome the problem of the conventional solder technology. However, the PCB cannot be used to load the current thin lead such that the leads of electric parts are arranged in an array type for enhancing the yield of manufacturing. However, a hollow solder and a curve PCB is occurred after soldering according to great number I/O leads and a small package volume. To solve the above problem is to lessen the volume of the jelly on the chip as small as possible.
As described above, the chip package technology trends toward Flip chip package. The process of flip chip package needs to grow multiple bumps on the wafer and each bump is electrically connected to the circuit on a PCB such that the top of each of the bumps face the PCB and the prerequisite condition of a open sensing area of the image sensor is limited. Consequently, the flip chip has a good electric property, heat dissipation and a small packaged size, but it is difficult to use the technology of flip chip on an image sensor very well.
A conventional flip chip package structure of an image sensor in accordance with the prior art shown in FIG. 7 comprises a glass plate (91) including an inner face forming a circuit (910) on the inner face of the glass plate (91) by etching. A chip (92) is soldered on the circuit near a middle portion of the glass plate (91) by using first tin balls (93) and the technology of flip chip. The circuit (910) of the glass plate (91) has two opposite sides each having a second tin ball (94) for surface mounting of the circuit (910). The diameter of each of the second tin ball (94) must be greater than the thickness of the chip (92) for a good reliability. For a suitable interval between the two second tin balls (94) the area of the glass plate (91) must be enlarged. Consequently, the enlarged glass plate (91) enlarges the volume of the image sensor. The type of the conventional flip chip package structure needs to be advantageously altered.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional flip chip package structure.